As ultra-large-scale-integrated circuit (ULSI) technology migrates to smaller lines widths, there are new challenges for the integration of conventional chemical mechanical polishing (CMP) processes. In addition, the introduction of low-k and ultra-low k dielectric films requires the use of a gentler CMP processes due to the films' low mechanical strength and weak adhesion to adjacent layers. Furthermore, ever-tightening defectivity specifications have placed additional demands on polishing slurries for low k films.
The integration of various low k films into USLIs can also require numerous extra steps and the incorporation of new technologies such as supercritical cleaning, dielectric and metal caps, conformal deposition of barriers and copper, chemical mechanical planarization with low down force and abrasive-free slurries. In addition to these technical options, ULSI fabricators must consider and address process complexity versus yield, reliability, mechanical strength, and performance, namely power dissipation from resistance-capacitance (RC) delay.
The complexities surrounding implementation of low k materials have introduced larger challenges for the barrier CMP process, which will necessitate the ability to control the complicated input variables and achieve a consistent high yield. Tuning process variables can contribute to decreasing polishing variation on the low k film. But the most desirable barrier CMP slurry will incorporate a low k dielectric-specific, surface activated agent that has process tunable performance adjustability. For example, Ye et al. in U.S. Pat. No. 6,916,742 disclose a slurry that adjusts the amount of polyvinyl pyrrolidone to control tantalum nitride and carbon doped oxide (CDO) removal rates. Adjusting the amounts of polyvinyl pyrrolidone and silica controls the ratio of tantalum nitride (barrier) to CDO (ultra low k dielectric) removal rates achieved with the slurry. Unfortunately, these slurries have inadequate copper removal rate for some applications.
There is a demand for a polishing slurry that can achieve the modular removal of barriers to ultra low k dielectrics with increased copper removal rates. Furthermore, there is a demand for a slurry that can remove a barrier with controlled dielectric erosion and controlled copper dishing.